Interlocking switching arrangement



April 14, 1931- c. w. HANSELL 1,800,525

INTERLOCKING SWITCHING ARRANGEMENT Filed March 22, 1927 2 Sheets-Sheet lINVENTOR C.W. HANSELL m film/M TORNEY April 14, 1931. c, w HANSELL Q1,800,525

INTERLOCKING SWITCHING ARRANGEMENT Filed March 22, 1927 2 Sheets-Sheet 2INVENTOR C.W HANSELL A TORNEY Patented Apr. 14, 1931 h f UNITED suresPATENT, OFFICE I .GLARENCEW. mivsELL, or Room? mmgm YoRK, ASSIGNOR To RAm o o onronii- TION or AMERICA, ACORPORATION or DELAWARE l INTEBLOCKINGswrromive ARRANGEMENT I Application file d March 22, 1927.} Seri'aljNo.177,377.

This invention relates to an interlocking switching arrangement, andmore particularly to such an arrangement applied to the circuitsassociated with electron emission tubes;

Y Y If'the full operating voltage is suddenly applied-to the filament ofan electron emission tube of large size the results may provedisastrous, for the filament sometimes breaks because of itsinability'to respond to the sudden expansion requirement placed uponit.-

Itis further stressed by reason of the'abnormal magnetic forces set up,inasmuch as the initial current flow is much greater thanthe 1 normaloperating current because of the re du'ced resistance of the filamentwhen cold.- It is an object of my invention to prevent the applicationof the full filament potential when the filament is cold. This I do byplac- 2o ing in-series with the operating-meansforf closing the filamentheating circuit ailimita ing contactor arranged to be closed'by thefil-- ament rheostat only when .the'resistance of the rheostat isentirely out in circuit.- Inthis' way, should the rheostat have beenleft out out of circuit when the filament circuit was last opened,'theoperating means are. made inoperative to close the circuit. Of course,after the filament circuit is enclosed the rheostatis substantially outout of circuit in order to bring the filament temperature up to itsnormal operating point.

' In such case, the limiting contactor will have opened. Nevertheless,the operating means -'jforthe filament circuit should at this time beoperative in order that the filament ciris at one of its extremeadjustments, will; nevertheless, be operative for the other of v itsfunctions.

plained hereinafter it is found that the electron velocities within thetube are greater is open, and the operating'means 1 4 is inoperative toclos'egthe switch S when the filament is at low than when at hightemperature. This high electron veof a circuit associated with anelectron emis-.

For reasons which will be more fully eX locity leads to excessive platetemperature. It-"also results in secondary emission from the grid, whichmay even be damaged by the high impact velocities. High electron veloc-.ities alsotend to cause ionization of any gas which may be present inthe tube, with ac companying'deleterious effect. To prevent thesedifficulties the anode potential should not be applied to the tube anodevuntil the filament has attained substantiallythenor Rial-operatingtemperature. It is a still further object of my invention to sointerlock the filament'and anode circuitsof an electron emission tubethat the operating means for opening or-closing the anode circuit willbe inoperative to close the anode circuit when Working range.

The specification 1 is accompanied a t t p v drawing in which- 7 Figure1 is a wiring diagram for a pre-.

ferred embodiment of my invention; and 5 Figure 2 is explanatory ofcertain" phe'-- nomena ineleotron emissiontubes. Referring to F igure 1of the drawing, the

electron emissiontubes 2 have filaments 4' which are-energized fromapower supply line 6,=which in this case has been represent? ed as analternating current supply, :but" which: may, of course, be a source ofdirect the filament temperature is'not within' its current. In serieswith-this supply thereis aZrelay operated switch. S and a filamentrheostat The rheostat R comprises resistanceelement 8 and a controlmeans 10 for cutting in or out more or less of the resistance 8. rWhenall of the resistance is cut in,-that is, when the control means 10 isat ,its.lowermost' position, it engages and closes the limitingcontactor 12.

The control switch 14 may be considered broadly anoperatingmeans foropening or. closing the power supply circuit; If the lim-I iting'contactor 12' is. depressed when-the operating means 14 is closed acircuit is esablished through the magnet ;16 which attracts the armature18', and: so closes the switch S If the resistanceJS is notentirelyoutin circuit then the. limiting contactor 12 err once the switch hasbeen closed, then if the rheostat control 10 is rotated to cut out partof the resistance 8, and the limiting con- 'tactor 12 opens,nevertheless the switch S will not be opened for the reason that acircuit is established through the ext raholdingcontactQZO which shortcircuits the limiting? contactor 12.

By the means so far described the operating means le -isinoperative toclose file ment heating circuit when-the filameifti rhe'o' stat is notentirely out in cirouit,or in other words, full filament potentialcannot beap plied to the filament when it, is cold, yet the. operatingmeans is always'elfective" the; filament heating circuit; V

In electron emission tube circuits-the anode? potential andth'eanodecurrent; are practiealmulch as the anode alternating; potentialexists 1 only with reference to a constant; directpo tential it' followsthat the actual? magnitude of the anode potential, with rfef-erenceg'to'truezero axis; at? the time the alternating anode: potential is mossnegative; is; really" highest: when the amplitude of alternatingpotential is'least- This-leads'to the appar-.

ently unexpected result that? highest electron velocities resultwhen"the anode alternating potential amplitude is least; for thevelocity;depends:- upon the" actualmagnitude of the} V attracting:- anodepotential, forgiven grid potenti alt This alternating: potential aniplitulde-i-s lowen at lower filament temperature: because-at that timethereis limited electron emissiom Tozfix the ideas reference is madetoFigure: 2 of the drawings, inwhich curve 501repre sents the gridpotential with: reference to: a holding potential 52; Theresultingta'node' current at normal filament temperature, and a lessercurrent for lower filament temperae t1ires; are 'shown'by: curves 5& and56: respectively. The steady anode potential is' 58;.

thenor'mal'. anode alternating .potent iaL ac companying anode current-54,- is?represented byfcurve 6V4; andPthesmaller amplitude:alter-'mating: anod'e pbtential, accompanying; anodecurrent: 56; is 1represented". by; curve 66; The actual; anode potential; at the time cof (also trlon flow, am -many "w but :with lower -filat-imerittemperatures is the greater value 12].:

It isitliereforek exceedingly desirable" to prevent the anode circuitfrom being closed before the filament temperature has been brought toits ordinary working range.

Again referring to Figure 1 of the drawing, the direct current supplyfor the anode cathodecircuit isobtained from a rectifier 26),,tp'j whichan alternating current'supply is led by way of the conductors 28. Inthis alternating current supply there is inserted a sweet S @h cou-rse;a direet -cu'rrent supply other than are'ctifier may be employed, and insome cases it might prove preferable to lodeterminant-switch S in thedirect current leads themselves. This switch S like S any" operatedby'means of a magnet 30 andhnopereiti-ng switch 32, which closes the relaymagnetacircuit, i To prevent its being closed; while the filament? is;cold: the anode; switch is interlocked: by the use of another limitingcontactor 34,: so located, as shown, that the rheostat control 10 must;substantialll-y out out the resist, 3110.8",8 before the limitingcontaetor 3.4: i's-x closed-L a V The filament rheostat B may be used:as a filament temperature control as Well as-;a startingresistance, forthereasonthat the? control 10. maybe backed fromthe; con;- tac'tor 34'once the switch S has beenclosed; This is; accomplished; by employing ahold ing contact 36,-: which shortcircuits-the-con factor 34;, V I .7 7

Although? the holding contacts 20 and 36 on: slwitches- S and S1; shortcircuit? the conmotors? 1-2 and 34;: nevertheless they do: notnot:limitation of my invention, which I"; 7

claim is: 1

1. In; combination, an electron emission tube, a starting rheostat forgradually buildin g up? the filament heating current therefor;

a circuit. associated with said tubegioperatinga means; for opening: orclosing said circuit;

miners" of. said cathode, a starting rheos'tafi, V

for gradually; building up. the potential. .ap? plied to the terminalsof said cathode, relay controlled operating means for opening orclosing; acircuit between said-- source andv cathode; and means tomakerarrela-y circuitof: said: operatingrm'eans inoperative for one ofs.its functions when? said starting; rheost'at;

is set near one of its extremities of adjustment. i

3. In combination, an electron emission tube, a filament heating circuitincluding a source of filament heating current, a starting rheostat forgradually building up the magnitude of said current, operating means foropening or closing the circuit, and means to make said operating meansinoperative to close said circuit when the resistance of the startingrheostat is partially and not fully in circuit. v

4:. In combination, an electron emission tube, a filament heatingcircuit including a source of filament heating current, a startingrheostat for gradually building up the magnitude of said current,operating means for opening or closing the circuit, and means to makesaid operating means always operative to open said circuit butinoperative to close said circuit when the resistance of the startingrheostat is partially and not fully in circuit. g

5. In combination, an electron emission tube, a cathode heating'circuttherefor including controlling means to control the cathode temperature,an anode circuit including operating means to open and close said anodecircuit, and means, responsive to the cathode temperature controllingmeans, for rendering the operating means inoperative to close the anodecircuit untilthe filament temperature has] been brought'substantially toits normal working temperature.

6. In combination, an electron emission tube, a cathode heating circuitincluding controlling means to control the cathode temperature, an anodecircuit .including operating means toopen and close said anode circuit,and means, responsive to the cathode temperature controlling means'forrendering the operating means operative to open the anode circuit andinoperative to close said circuit until the cathode temperature has beenbrought substantially to its normal working temperature. Y

7. In COIIIblIlfl/GlOIl, an electron emission tube, a filament heatingc1rcu1t including a,-

rheostat for controlling the heating current, an anode circuit, a sourceof anode current, operating means to connect and disconnect said sourceand said anode circuit, and means to make the operating meansinoperative to connect the source and the anode circuit when thefilament rheostat is not substantially cut out of circuit.

8. An interlocking switching arrangement for an electron emission tubeand its associated cathode and anode circuits comprising operating meansto open and close said cathode operating means upon substantialinclusion of the rheostat resistance in circuit, thereby preventingsudden heating of the cathode, and, means responsive to the movement of:said rheostat for rendering operative said anode. operating means uponremoval of the rheostat resistance from the cathode circuit.

9; In combination, an electron emission tube having a heated cathode, aheating circuit including a starting rheostat for grad- 'ually applyingthe heating current, a relay operated switch for opening and closing theheating circuit, operating means for the relay, and means to make theoperating means inoperative to close the switch when the resistance ofthe starting rheostat is not fully in circuit.

tive to close. the switch when the starting rheostat is notsubstantially cut out of circuit.

11. An interlocking switching arrange- ,ment comprising an electronemission tube vhaving an anode and a heated cathode, a

heating circuit including a starting rheostatfor gradually applying theheating current, a firstorelay operated switch for opening and closingthe heating circuit, an anode circuit, a source of anode current, asecond relay operated' switch for connecting and disconnecting saidsource and said anode circuit, operating means for the relays, and meansto make the operating means inoperative to close the first switch whentheresistance of the rheostat is not fully in circuit, and inoperativeto close the second switch when the rheostat is not substantially cutout of circuit.

.12. In combination, an electron emission tube, means for graduallybuilding up the cathode heating current therefor, a circuit associatedwith the tube, operating means for opening or closing said circuit, andmeans to make said operating means inoperative for one of its functionswhen said current building up means is set near one of its extremes ofadjustment even though not open circuited.

CLARENCE W. HANSELL.

